The present invention is generally directed to an improved core for holding web material and in particular to a core for holding film within a film cartridge.
Cores for holding web material are well known in the art with such devices finding considerable application in film cartridges for microfilm readers.
In the use of film spools, for example, it is customary to wind film upon the spool by positioning one end of the film through a slot formed in the hub so that the film end may be at least momentarily held while the first few strands of film are wound.
The winding of film on reels has presented a problem because of the tendency of the core terminal portion of the strip of film to slip about the hub of the reel on which it is to be wound at the start of the rotational movement of the reel. The provision of a threading slot extending transversely through the hub of a reel, through which the film can be threaded, has proved to be insufficient to hold the end of the film at the start of the rotational movement of the reel on which the film is to be wound. The pulling force exerted on the strip of film at the start of the rotational movement of the reel pulls the end of the film out of the threading slot, unless some additional means is provided for holding the film end until the overlapping of the succeeding film convolutions establishes sufficient frictional restraint to prevent relative sliding movement between adjacent convolutions.
While film cores in the past have been generally successful, they have been relatively complicated and expensive to produce, requiring a number of individual parts. In fabricating such cores, it thereby becomes necessary to fabricate more than one part and to assemble the parts with the film in order to provide a complete cartridge.
It is, therefore, a general object of the present invention to provide a newly designed and improved core for holding web material.
It is a more specific object of the present invention to provide a newly designed and improved core for holding microfilm within a microfilm cartridge.
Additionally, it is a further object of the present invention to provide a core for holding film material which securely holds the film and which includes only a single part, thus rendering the improved core less expensive as to manufacture.
Additionally, it is a further object of the present invention to prevent separation of the microfilm from the cartridge core of an unwound reel during unwinding operations.